Agriculture Reference
In-Depth Information
WHAT YOU'LL NEED
• 15 to 20 healthy, flowering plants
• insect netting (or absence of cabbage pests)
• trellis or one support pole per flowering plant
• for winter radishes: overwintering strategy
POLLINATION NOTES
Radishes are insect pollinated and, like all brassicas, are self-infertile outcross-
ers: a flower from one plant can only be pollinated by a flower from another plant. Since summer and
winter radishes belong to the same species, they can cross with one another; they do not, however,
cross with other brassicas like cabbage or turnip. Flowers are normally white or off-white, often with
purple veins. Even pure varieties can produce variably colored flowers. Make sure there are plenty of
plants flowering at once to reduce the risk of inbreeding. The more plants that flower next to each oth-
er, the greater the seed yield will be. Isolate multiple varieties of this species by at least 500 ft. (150
m). Isolation distances should be much greater ( mile [500 m] or more) when larger quantities are be-
ing grown and when garden configuration is less than ideal (few or no tall plants, one variety down-
wind from another variety, etc.). Temporal isolation can be achieved by growing, for example, a winter
radish variety and a summer radish variety and choosing sowing times that ensure that the two do not
flower at the same time. Otherwise, isolate mechanically by growing in cages.
Radish seeds
Most summer radishes have white flowers. Their cylindrical seedpods stand upright and do not explode when ripe.
GROWING FOR SEED
Summer radishes produce ripe seeds in one growing season. The German heir-
loom 'Mairettich' is an in-between form that also produces seed the first year. Winter radishes are
grown for seed as biennials. Summer radishes are very easy to grow for seed and are an ideal crop for
the beginning seed saver. Sowing in early to mid spring makes for ripe seed in late summer to early au-
tumn. Cover radish seed only lightly with soil. When seed is planted too deeply, radishes turn out mis-
shapen. A round radish planted even only in. (1.5 cm) deep will develop into a cylinder instead. For
this reason, when growing radishes for seed, sow seed in pots or trays on the surface. Observe their de-
